1. Field of the Invention
The present invention relates to liquid crystal cell assemblies for liquid crystal displays (LCDs) and, more particularly, to a liquid crystal cell assembly for LCDs with alignment films.
2. Description of Related Art
Because LCDs have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCDs are considered to have the potential to completely replace cathode ray tube (CRT) monitors and televisions.
Referring to FIG. 4, a conventional liquid crystal cell assembly 100 for LCDs generally includes a first base plate 104, a second base plate 112, and a liquid crystal layer 118 located between the two base plates 104 and 112. An alignment layer 108 is formed on an inner surface of the first base plate 104 and a first transparent electrode layer 106 is formed therebetween. A first polarizer 102 is formed on an outer surface of the first base plate 104. An alignment layer 116 is formed on an inner surface of the second base plate 112 and a second transparent electrode layer 114 is formed therebetween. A second polarizer 110 is formed on an outer surface of the first base plate 112.
The liquid crystal layer 118 includes a plurality of rod-like liquid crystal molecules 1182. A plurality of parallel fine grooves 1082 is formed on an inner surface of the alignment layer 108. A plurality of parallel fine grooves 1162 are formed on an inner surface of the alignment layer 116. The grooves 1082 and 1162 function so as to align the orientation of the liquid crystal molecules 1182, i.e., to align the liquid crystal molecules 1182 adjacent to the alignment layers 108 and 116 parallel to the grooves 1082 and 1162 respectively. When the grooves 1082 and 1162 are at right angles and the base plates 104 and 112 are at appropriate spacing, the liquid crystal molecules 1182 can automatically turn 90 degrees from top to bottom.
The alignment layers 108 and 116 are important to the liquid crystal cell assembly 100. Alignment qualities of the alignment layers 108 and 116 are one of the key factors that determine the display quality of the liquid crystal cell assembly 100. The alignment layers 108 and 116 can be made using a rubbing method. The rubbing method can be exemplified using the manufacturing method for the alignment layer 116 as below. The manufacturing method for the alignment layers 116 generally includes the steps of: coating a layer of alignment material, such as polyimide, on the inner surface of the second transparent electrode layer 114; and rubbing the surface of the alignment material using rubbing cloth to form the plurality of fine grooves 1162.
However, some drawbacks arise from a mechanical contact of the rubbing cloth with the surface of the alignment material. This method is complicated because a baking process of the polyimide layer takes long time, and the rubbing introduces large electrostatic charges as well as plenty of dust contamination, which in turn needs other facilities and rinse processes to eliminate. In addition, the rubbing cloth has a limited lifespan and needs to be replaced frequently.
The polarizers 102 and 110 and the transparent electrode layers 106 and 114 play an important role in making the liquid crystal cell assembly 100 display images. However, the polarizers 102 and 110 and the transparent electrode layers 106 and 114 may make the liquid crystal cell assembly 100 thicker and reduce the transparency of the liquid crystal cell assembly 100. Moreover, the polarizers 102 and 110 and the transparent electrode layers 106 and 114 may increase the cost for manufacturing the liquid crystal cell assembly 100.
What is needed, therefore, is a liquid crystal cell assembly with a good alignment quality and a thin structure.